Synchronized operation system for numerical control apparatus

ABSTRACT

A synchronized operation system by which a plurality of independently controlled numerical control apparatuses (CNCs) are made to carry out a synchronized operation. An external signal generation circuit (1) supplies an external timing signal to respective CNCs (2,3), from the outside, and internal signal generation circuits (10, 20) generate internal timing signals for independently operating the CNCs (2, 3). Selection circuits (9, 19) select one of the external timing signals and the internal timing signal, and when the external timing signal is selected, the respective CNCs (2, 3) are operated by using the selected external timing signals as basic timing signals. Therefore, no time lag occurs between the basic timing signals of the respective CNCs (2, 3) an and thus the respective CNCs (2, 3) can carry out an extremely a closely synchronized operation, such as an interpolation, based on the basic timing signals.

TECHNICAL FIELD

The present invention relates to a synchronized operation system usedfor controlling a plurality of numerical control apparatuses (CNCs), andmore specifically, to a synchronized operation system for CNCs by whicha plurality of independently controlled CNCs are made to carry out asynchronized operation.

BACKGROUND ART

Numerical control apparatuses (CNCs) are used at each station of atransfer line for machining parts for automobiles, and these CNCscontain a programmable machine controller (PMC) for controlling only asingle axis. The CNCs of this type are referred to as a single-axisCNCs.

Although these single-axis CNCs are usually independently controlled,sometimes a plurality of single-axis CNCs must be simultaneouslycontrolled for performing various operations, i.e., cutting an arc, andto accomplish this, the I/O circuits of the respective CNCs areinterconnected and data is exchanged through the I/O circuits.

Nevertheless, when data is exchanged through the I/O circuits, in theoperation of the respective CNCs, a time lag occurs and further,communication therebetween becomes complicated, and as a result, a highaccurate synchronized operation, such as an interpolation, cannot becarried out.

SUMMARY OF THE INVENTION

Taking the above into consideration, an object of the present inventionis to provide a synchronized operation system for CNCs by which anaccurate synchronized operation, such as an interpolation, can becarried out among a plurality of CNCs.

To attain the above object, according to the present invention, there isprovided a synchronized operation system for CNCs by which a pluralityof independently controlled numerical control apparatuses (CNCs) aremade to carry out a synchronized operation, the system comprising anexternal signal generation means for supplying an external timing signalto each of the CNCs, from the outside, an external signal receivingmeans for receiving the external timing signal, an internal signalgeneration means for generating an internal timing signal, to operatethe CNCs independently, and a basic timing signal selection means forselecting one of the external timing signal received from the externalsignal receiving means and the internal timing signal received from theinternal signal generation means and supplying the selected signal tothe CNCs as a basic timing signal.

The external signal generation means supplies an external timing signalto the respective CNCs, from the outside, and the external signalreceiving means receives the external timing signal. The internal signalgeneration means generates an internal timing signal for operating theCNCs independently, and the basic timing signal selection means selectsone of the external timing signal received from the external signalgeneration means and the internal timing signal received from theinternal signal generation means, and supplies the selected signal tothe CNCs as a basic timing signal.

As a result, after the basic timing selection means has selected theexternal timing signal, the respective CNCs are operated by using theexternal timing signal as a basic timing signal. Accordingly, no timelag occurs among the basic timing signals for the respective CNCs, andthus the respective CNCs can be operated while closely synchronized witheach other, and can cooperate to carry out even a high accuratesynchronized operation, such as an interpolation, based on the basictiming signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the arrangement of a synchronizedoperation system for CNCs according to the present invention; and

FIG. 2 is a diagram showing another embodiment according to the presentinvention.

DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described below withreference to the drawings.

FIG. 1 is a schematic diagram showing the arrangement of a synchronizedoperation system for CNCs according to the present invention, wherein anexternal ITP signal generation circuit 1 supplies an external ITP signalto a plurality (here, 2 sets) of CNCs 2 and 3. Note, the ITP(interpolation) signal is a timing signal for performing aninterpolation.

The external ITP signal generation circuit 1 may be contained in a CNCdifferent from the CNCs 2 and 3; with this arrangement, the differentCNC can be operated as a master CNC and the CNCs 2 and 3 each can beoperated as a slave CNC.

Further, the external ITP signal generation circuit 1 may be arranged asan independent circuit unit.

The external ITP signal is output through the connectors 4 and 5 of theITP signal generation circuit 1 and input to the respective CNCs throughthe connector 6 of the CNC 2 and the connector 7 of the CNC 3,respectively. This external ITP signal is obtained by dividing a clockcontained in the external ITP signal generation circuit 1.

Since the CNCs 2 and 3 are single-axis CNCs and have the samearrangement, only the CNC 2 will be described here.

The external ITP signal supplied to the CNC 2 is received by an externalITP signal receiving circuit 8, and is supplied to a selection circuit 9by the receiving circuit 8.

An internal ITP signal generation circuit 10 supplies an internal ITPsignal to the selection circuit 9. The internal ITP signal is obtainedby dividing the clock contained in the internal ITP signal generationcircuit 10, in the same way the external ITP signal is generated.

The selection circuit 9 receiving the external ITP signal and theinternal ITP signal is connected to a key switch 11 which is providedfor selecting one of the external ITP signal and internal ITP signal andis actuated by an operator.

When the external ITP signal is selected by the key switch 11, theselection circuit 9 selects the external ITP signal, and when theinternal ITP signal is selected by the key switch 11, the selectioncircuit 9 selects the internal ITP signal. The signal selected by theselection circuit 9 is output therefrom as a basic ITP signal of the CNC2.

Further, the selection circuit 19 of the CNC 3 selects one of theexternal ITP signal and an internal ITP signal, in the same way as theselection circuit 9 of the CNC 2, and outputs the selected signal as abasic ITP signal of the CNC 3.

When the basic ITP signals are external ITP signals, the basic ITPsignals of the CNCs 2 and 3 have no time lag, and thus the CNCs 2 and 3can be operated while being closely synchronized with each other basedon the basic ITP signals, and therefore, the CNCs 2 and 3 can cooperateto carry out even highly accurate synchronized operation such as aninterpolation.

In this case, a communication line conventionally provided between theCNCs 2 and 3 for a high accurate synchronized operation thereof is notnecessary, and thus the communication relationship therebetween can besimplified.

When the basic ITP signals are internal ITP signals, the CNCs 2 and 3are controlled independently, based on the respective internal ITPsignals.

FIG. 2 is a diagram showing another embodiment according to the presentinvention. This embodiment is different from the first embodiment inthat a monitor circuit 12 is used in place of the key switch 11. Themonitor circuit 12 comprises of, for example, a watch dog timer, anddetermines whether or not the state in which an external ITP signal isreceived has been changed, by monitoring the external ITP signalreceiving circuit 8.

A selection circuit 9 selects one of an external ITP signal and internalITP signal, based on the result of the determination of the monitorcircuit 12. More specifically, when the external ITP signal receivingcircuit 8 receives the external ITP signal, the selection circuit 9selects the external ITP signal, and when the external ITP signalreceiving circuit 8 does not receive the external ITP signal, theselection circuit 9 selects the internal ITP signal.

As described above, the use of the monitor circuit 12 allows anautomatic change of a basic ITP signal output from the selection circuit9.

Although the above description refers to a case in which 2 sets of CNCsare used, the present invention can be applied in the same way to a casein which more than 2 sets of CNCs are used.

As described above, according to the present invention, since therespective CNCs are operated by using external ITP signals as basic ITPsignals, no time lag occurs between the basic ITP signals of therespective CNCs, and thus the respective CNCs can be operated whilebeing closely synchronized with each other, based on the basic ITPsignals and, as a result, the CNCs can cooperate to carry out a highaccurate synchronized operation such as an interpolation.

I claim:
 1. A synchronized operation system by which a plurality of independently controlled numerical control apparatuses are made to carry out a synchronized operation, said synchronized operation system comprising:external signal generation means for supplying an external timing signal to each of said plurality of independently controlled numerical apparatuses, from the outside; and each of said plurality of independently controlled numerical control apparatuses comprising:external signal receiving means for receiving said external timing signal; internal signal generation means for generating an internal timing signal for operating the respective one of said plurality of independently controlled numerical control apparatuses independently; and basic timing signal selection means for selecting one of said external timing signal received from said external signal receiving means and said internal timing signal received from said internal signal generation means of the respective one of said plurality of independently controlled numerical control apparatuses, to generate a selected signal and supplying said selected signal to the respective one of said plurality of independently controlled numerical control apparatuses as a basic timing signal.
 2. The synchronized operation system according to claim 1, wherein each of said basic timing signal selection means selects one of said external timing signal and said internal timing signal of the respective one of said plurality of independently controlled numerical control apparatuses in accordance with a selection made by using a key switch.
 3. The synchronized operation system according to claim 1, wherein each of said basic timing signal selection means selects said external timing signal when said external timing signal is received and selects said internal timing signal of the respective one of said plurality of independently controlled numerical control apparatuses when said external timing signal is not received, in accordance with a result of a monitoring carried out by a monitor means for monitoring said external timing signal.
 4. A synchronized operation system for CNCs according to claim 1, wherein said external signal receiving means, said internal signal generation means and said basic timing signal selection means are provided within each of said CNCs.
 5. The synchronized operation system according to claim 1, wherein each of said external timing signal and said internal timing signals is an interpolation signal.
 6. The synchronized operation system according to claim 1, wherein each of said plurality of independently controlled numerical control apparatuses is a single-axis numerical control apparatus.
 7. The synchronized operation system according to claim 1, wherein said external signal generation means is contained in a numerical control apparatus other than one of said plurality of independently controlled numerical control apparatuses.
 8. The synchronized operation system according to claim 1, wherein each of said plurality of independently controlled numerical control apparatuses further comprises:key switch means for receiving an input from an operator, and controlling said basic timing signal selection means of the respective one of said plurality of independently controlled numerical control apparatuses in dependence upon said input from the operator.
 9. The synchronized operation system according to claim 1, wherein each of said plurality independently controlled numerical control apparatuses further comprises:monitor means for determining a state of said external timing signal and controlling said basic timing signal selection means of the respective one of said plurality of independently controlled numerical control apparatuses to select one of said internal timing signal of the respective one of said plurality of independently controlled numerical control apparatuses and said external timing signal in dependence upon said determination.
 10. The synchronized operation system according to claim 9, wherein each of said monitor means comprises:a watchdog timer.
 11. The synchronized operation system according to claim 9, wherein each of said monitor means controls said basic timing signal selection means of the respective one of said plurality of independently controlled numerical control apparatuses to select said external timing signal if said external signal is received by said each monitor means and controls said basic timing signal selection means of the respective one of said plurality of independently controlled numerical control apparatuses to select said internal timing signal of the respective one of said plurality of independently controlled numerical control apparatuses if said external signal is not received by said monitor means. 